Fig. 2

Spectroscopic and statistical analysis on lipids. Spectra were acquired using SR-FTIR on normal livers as controls (n = 5), cirrhosis and their corresponding HCC (n = 3). All spectra were baseline corrected within the 3000–2840 cm⁻¹ region. Principal component analysis (PCA) was performed on spectra from a normal livers, cirrhosis and HCC or b only from cirrhosis and HCC. The score plot based on PC1 and PC2 is shown where each point represents one spectrum. c The average spectra corresponding to normal liver, cirrhosis and HCC tissues were extracted. d The ratio of two main peak areas corresponding to C–H asymmetric stretch of CH₂/CH₃ within each group of tissue was calculated and plotted as boxplot. Unpaired Student t test was applied between control and cirrhosis/HCC. *: unpaired t test, p < 0.05